How the Zeo sleep device works around the limitations of home monitoring

The Zeo is part of a trend toward using technology to monitor our own bodies. People have always been concerned about their health, of course, and have tried different things to see what works (including rather absurd superstitions). But now there are ways to bolster one's curiosity with real scientific data.

The Zeo makes this data available for people who may have sleep problems--and quite a lot do, judging from a 2005 National Sleep Foundation (NSF) poll (a recent poll covering a wide range of adults):

26% say they had "a good night's sleep" only a few nights a month or less. Another 24% report having "a good night's sleep" a few nights a week.

This blog is meant to be a technical discussion, not a consumer guide, so I took the opportunity to talk to Ben Rubin, CTO and cofounder of Zeo, just a couple weeks after the official release of the Zeo to get some information on two aspects:

• How it collects data during sleep
• How they analyze the data to help the customer sleep better

The Zeo sensor device is a simple headband with a silver layer that lies on your forehead. The designers chose silver because it doesn't cause allergic reactions and efficiently picks up electronic waves with minimal noise from sweat or other interference.

The electrical signals given off by the brain, the eyes, and muscle movements around the face are collected 128 times per second. Activity at different frequencies indicates what kind of sleep you're in (if any), in ways well known to sleep researchers. For instance:

• Activity in the 11 to 14 Hz range indicate some form of sleep. Spikes in that range--sleep spindles--indicate light sleep.
• Activity in the 2-4 Hz range (Delta waves) indicate deep sleep.
• REM sleep has less in the Delta range and more in higher frequencies, along with the heightened eye movements that give the sleep phase its name, and fewer muscle contractions, which can be measured by activity in the 30 Hz range.

And so forth. The headband knows the essential frequencies of electronic activity in the brain, in the eyes (because they're electronically polarized) and in the facial muscles. This is quite impressive when you look at traditional sleep labs. They put sensors on many different parts of the face to get their data. In contrast, the Zeo picks up a signal that it has to separate into frequency bands. Of course, the lab is more accurate, but its cost makes it feasible only for diagnosed sleep disorders. (The Zeo company wants to make it clear that they aren't providing a medical device and don't offer diagnoses.)

Samples are run through a Fast Fourier Transform and more complex, proprietary algorithms every 30 seconds to get data that the Zeo device on your bedstand accumulates. It can tell you later how many hours you spent in each phase of sleep. Every five minutes, another calculation determines what phase you're in (light, REM, deep, or awake) and displays a band on an LED screen so you can check the pattern of your sleep when you wake up. (In the figure, the bands indicating heaviness of sleep appear near the bottom of the screen.)

The calculations used by the Zeo were developed through a neural network trained on huge numbers of people, both normal sleepers and troubled sleepers. In effect, the algorithms were refined by comparing their output to the analysis of sleep experts for each person who joined the experiment. (Rubin was one of the guinea pigs, along with many other staff. That was probably the most sleep any of them got during their work in this start-up.)

Zeo ran an experiment in which sleepers were simultaneously monitored by a prototype of the Zeo, by an older technology called an actigraph, and by sleep researchers using a polysomnograph. The calculations by the Zeo prototype came fairly close to the accuracy of the other forms of measurement. For instance, the machine agreed with researchers about 75% of the time about the difference between light sleep, REM sleep, and deep sleep. This looks pretty good when you learn that the two sleep researchers agreed with each other 85% of the time.

The goal of marketing the Zeo, of course, is to help people benefit from their new knowledge. Typically, a customer records sleep for a week, along with information about his lifestyle and related information (such as whether family members woke him up). Zeo offers a web site where customers can record this data, which was developed through partnerships with the world's leading sleep researchers and consists of fairly standard questions: Are you stressed? Did you drink caffeine or alcohol in the evening? How do you feel when you first wake up?

The web site processes the data and makes recommendations, based on well-understood findings in the field of sleep research, about what you can change to improve to sleep. Another program you can sign up for--Sleep Coach--compares the personal behavior you report with your sleep patterns and makes more targeted recommendations.

Naturally, technologically sophisticated users want to get their hands on their own data. Zeo has responded by offering customers data--starting yesterday--in a CSV format. And there's no reason that people can't share their data in order to search for new patterns in a crowdsourcing manner, like the well-known PatientsLikeMe site.

Our new sensitivity to health issues is sure to draw in companies with technological solutions. WIRED Magazine profiled the Nike+ sensor and Internet recording system, and a company named Withings recently announced a WiFi-primed body weight scale that records your weight, body fat content, and BMI to a web site (rather slim benefits for $160, it seems to me). Someday we may even be able to monitor many of the medical signs that currently require blood work through a device placed on the eye.

These, along with Zeo, are examples where instant feedback and the ability to track trends over time can change our whole attitude toward our bodies. Fitness is no fad; we are recognizing the serious effects lifestyle can have on our long-term happiness and ultimately our economic output. Going deeper, it's about time that computer technology, which for so long has kept us immobile in our chairs and divorce us from the physical world, made a 180° turn to put us more in touch with our bodies and the reality around us.

So far as the Zeo goes, I pondered the value of the data it offers when you're considering life style choices. Do you really need a machine to push you into giving up coffee or turning off the TV earlier in the evening?

I think data can help, because different people are affected by lifestyle decisions in different ways. There's no reason to kick the dog out of your bedroom or give up that cherished glass of Chianti you have with your lasagna dinner if it really isn't bothering you. That's the value of feedback: we can link our behavior to an outcome and make rational choices. It's easier to act healthy if you know you're not just being superstitious.